The ability to selectively alter the mouse genome through gene transfer (transgenic mice), homologous recombination (gene targeting) and chemical mutagenesis is providing new and powerful tools for biomedical research. The production and use of transgenic mice has rapidly expanded since its inception in 1980 and, although a relatively new technology, gene targeting promises to develop as swiftly. Recently, scientists have expressed concerns about the preservation, health and free distribution of these animals. These mice represent an extremely valuable biomedical resource and they must be protected against accidental loss. Researchers are receiving numerous requests for mice they have produced and the free exchange of mice between colonies of varying health status may pose a threat to the health of all research colonies, worldwide. In addition, many researchers who produce these mice want to be relieved of the responsibility for their distribution. The Jackson Laboratory has maintained, preserved and distributed inbred strains and mutant stocks for over 60 years. The Laboratory has created a number of genetic resources that identify, maintain and distribute important mutant mice. Recently the Laboratory established the Induced Mutant Resource (IMR) whose purpose is to import, cryopreserve and distribute biomedically important transgenic, targeted and chemically induced mutant mice. The purpose of this application is to seek funds for the importation and cryopreservation of transgenic and targeted mutant mice. These mice will then be freely distributed to the scientific community on a cost recovery basis. By serving as a National Resource for Transgenic and Targeted mice, the Jackson laboratory will provide for the health, preservation and distribution of these important biomedical animals.